In the area of digital imaging, a pixel (or picture element) is usually the smallest item of information in an image. Pixels are normally arranged in a two-dimensional gird and are often represented using dots or squares. Each pixel is a sample of an original image, where more samples typically provide more accurate representations of the original image. The intensity of each pixel is usually variable. In electronic color displays, such as flat-panel televisions, each pixel has typically three or four components. A three component pixel may have, for example, red, green and blue components. A four component pixel may have, for example, cyan, magenta, yellow and black components.
Color components are usually LEDs (Light Emitting Diodes). LEDs are usually based semiconductor diode chips. When a semiconductor diode chip is forward biased, electrons recombine with holes and energy is released in the form of light. This effect is called electroluminescence. The color of the light is determined by the energy gap of the semiconductor diode chip. The semiconductor diode chip is usually small in area, often less than 1 mm2. A package that contains a semiconductor diode chip is usually larger than the semiconductor diode chip. For example, the diameter of a discrete packaged LED may be 4 or 5 mm.
A FCD (full color display) board typically uses discrete color LEDs to form a pixel. A FCD board is usually a very large video screen such as those used in baseball stadiums, arena events, music events and large format advertising on the side of buildings. Because FCD boards are often used outdoors, sunlight reflected into an LED can reduce the contrast (the difference in brightness between one pixel and another pixel) of the display. For example, sunlight reflected into an “off” pixel can cause the “off” pixel to appear brighter than it would have with no sunlight reflected into the off pixel.